An RFID system includes an RFID reader and at least one RFID tag. FIG. 1 shows a structural diagram of a conventional RFID tag 100. The RFID tag 100 comprises an RF receiver 101, an RF transmitter 103, a storage device unit 105 and a control circuit 107. The RF receiver 101 and the RF transmitter 103 receive from or transmit to the RFID reader messages and data. The control circuit, e.g., a processor or a circuit with operational capabilities, responds to requests from the reader, and controls operations of other elements. The storage device unit 105 stores specific data.
FIG. 2 shows a state flow of an RFID tag, which is controlled by an RFID reader to enter different states. As shown, the state flow comprises a ready state, an arbitrate state, a reply state, an acknowledged state, an open state, a secured state and a killed state. In the ready state, supposing the RFID tag is a passive RFID tag, it means that the RFID tag generates power from received signals. The RFID tag then receives a command from the RFID reader and enters the arbitrate state. Only one of the RFID tags is selected to enter the states subsequent to the reply state, while other RFID tags await in the arbitrate state. In the acknowledged state, the RFID reader sends an identification code, such as Handle in this example, for identification when the RFID reader accesses data.
Generally speaking, the foregoing ready, arbitrate, reply, and acknowledged operations are preparatory steps for accessing the RFID tag. After the open state and the secured state, the RFID tag enters an accessible state. In the open state, only a part of the data stored in a first RFID tag is accessible. In the secured state, the RFID tag needs to receive a specific code before more stored data therein can be accessed. Once having been fully accessed, the RFID tag returns to the ready state. Referring to FIG. 2, the RFID tag skips the acknowledged state and directly enters the secured state from the open state. Alternatively, the RFID tag skips the open state and directly enters the secured state from the acknowledged state. Detailed operations of accessing an RFID tag are known to a person having ordinary skill in the art, and thus shall not be unnecessarily further discussed.
An RFID system mainly serves for identification purposes; that is, identification data is stored in the storage device unit 105 of the RFID tag 100, and the identification data is then read by an RFID reader. However, as performance of the control circuit 107 of the RFID tag 100 improves, system resources capable of executing more complex tasks would be wasted if the RFID were to merely serve as an identification device.